CFR-2011-title29-vol8-sec1926-57

7/29/2019 CFR-2011-title29-vol8-sec1926-57

1/26

49

Occupational Safety and Health Admin., Labor 1926.57

TABLE D3MINIMUM ILLUMINATION INTENSITIESIN FOOT-CANDLESContinued

Foot-candles Area or operation

10 ...................... General construction plant and shops(e.g., batch plants, screening plants,mechanical and electrical equipmentrooms, carpenter shops, rigging loftsand active storerooms, barracks or liv-ing quarters, locker or dressing rooms,mess halls, and indoor toilets and work-rooms).

30 ...................... First aid stations, infirmaries, and offices.

(b) Other areas. For areas or oper-ations not covered above, refer to the

American National Standard A11.11965, R1970, Practice for IndustrialLighting, for recommended values of il-lumination.

1926.57 Ventilation.

(a) General. Whenever hazardous sub-stances such as dusts, fumes, mists, va-pors, or gases exist or are produced inthe course of construction work, theirconcentrations shall not exceed thelimits specified in 1926.55(a). Whenventilation is used as an engineeringcontrol method, the system shall be in-stalled and operated according to therequirements of this section.

(b) Local exhaust ventilation. Local ex-

haust ventilation when used as de-scribed in (a) shall be designed to pre-

vent dispersion into the air of dusts,fumes, mists, vapors, and gases in con-centrations causing harmful exposure.

Such exhaust systems shall be so de-signed that dusts, fumes, mists, vapors,or gases are not drawn through the

work area of employees.(c) Design and operation. Exhaust

fans, jets, ducts, hoods, separators, andall necessary appurtenances, includingrefuse receptacles, shall be so designed,

constructed, maintained and operatedas to ensure the required protection bymaintaining a volume and velocity of

exhaust air sufficient to gather dusts,

fumes, vapors, or gases from saidequipment or process, and to convey

them to suitable points of safe dis-posal, thereby preventing their disper-sion in harmful quantities into the at-

mosphere where employees work.(d) Duration of operations. (1) The ex-

haust system shall be in operation con-tinually during all operations which it

is designed to serve. If the employee re-mains in the contaminated zone, the

system shall continue to operate after

the cessation of said operations, thelength of time to depend upon the indi-vidual circumstances and effectiveness

of the general ventilation system.(2) Since dust capable of causing dis-

ability is, according to the best med-

ical opinion, of microscopic size, tend-ing to remain for hours in suspensionin still air, it is essential that the ex-

haust system be continued in operationfor a time after the work process orequipment served by the same shallhave ceased, in order to ensure the re-

moval of the harmful elements to therequired extent. For the same reason,employees wearing respiratory equip-

ment should not remove same imme-diately until the atmosphere seemsclear.

(e) Disposal of exhaust materials. Theair outlet from every dust separator,and the dusts, fumes, mists, vapors, or

gases collected by an exhaust or ven-tilating system shall discharge to theoutside atmosphere. Collecting sys-

tems which return air to work areamay be used if concentrations whichaccumulate in the work area air do not

result in harmful exposure to employ-ees. Dust and refuse discharged from an

exhaust system shall be disposed of insuch a manner that it will not result inharmful exposure to employees.

(f) Abrasive blasting(1) Definitions

applicable to this paragraph(i) Abra-

sive. A solid substance used in an abra-sive blasting operation.

(ii) Abrasive-blasting respirator. A res-pirator constructed so that it coversthe wearers head, neck, and shoulders

to protect the wearer from reboundingabrasive.

(iii) Blast cleaning barrel. A complete

enclosure which rotates on an axis, orwhich has an internal moving tread totumble the parts, in order to exposevarious surfaces of the parts to the ac-

tion of an automatic blast spray.(iv) Blast cleaning room. A complete

enclosure in which blasting operations

are performed and where the operatorworks inside of the room to operate theblasting nozzle and direct the flow of

the abrasive material.(v) Blasting cabinet. An enclosure

where the operator stands outside and

operates the blasting nozzle through anopening or openings in the enclosure.

VerDate Mar2010 15:51 Sep 16, 2011 Jkt 223116 PO 00000 Frm 00059 Fmt 8010 Sfmt 8010 Q:\29\29V8.TXT ofr150 PsN: PC150

7/29/2019 CFR-2011-title29-vol8-sec1926-57

2/26

50

29 CFR Ch. XVII (7111 Edition) 1926.57

(vi) Clean air. Air of such purity that

it will not cause harm or discomfort toan individual if it is inhaled for ex-tended periods of time.

(vii) Dust collector. A device or com-bination of devices for separating dustfrom the air handled by an exhaust

ventilation system.(viii) Exhaust ventilation system. A

system for removing contaminated air

from a space, comprising two or moreof the following elements (A) enclosureor hood, (B) duct work, (C) dust col-lecting equipment, (D) exhauster, and

(E) discharge stack.(ix) Particulate-filter respirator. An air

purifying respirator, commonly re-

ferred to as a dust or a fume respirator,which removes most of the dust orfume from the air passing through the

device.(x) Respirable dust. Airborne dust in

sizes capable of passing through the

upper respiratory system to reach thelower lung passages.

(xi) Rotary blast cleaning table. An en-

closure where the pieces to be cleanedare positioned on a rotating table andare passed automatically through a se-

ries of blast sprays.(xii) Abrasive blasting. The forcible

application of an abrasive to a surfaceby pneumatic pressure, hydraulic pres-sure, or centrifugal force.

(2) Dust hazards from abrasive blasting.

(i) Abrasives and the surface coatingson the materials blasted are shatteredand pulverized during blasting oper-

ations and the dust formed will containparticles of respirable size. The com-position and toxicity of the dust from

these sources shall be considered inmaking an evaluation of the potentialhealth hazards.

(ii) The concentration of respirabledust or fume in the breathing zone ofthe abrasive-blasting operator or anyother worker shall be kept below the

levels specified in 1926.55 or other per-tinent sections of this part.

(iii) Organic abrasives which are

combustible shall be used only in auto-matic systems. Where flammable or ex-plosive dust mixtures may be present,

the construction of the equipment, in-cluding the exhaust system and allelectric wiring, shall conform to the

requirements of American NationalStandard Installation of Blower and

Exhaust Systems for Dust, Stock, and

Vapor Removal or Conveying, Z33.11961 (NFPA 911961), and subpart S ofthis part. The blast nozzle shall be

bonded and grounded to prevent thebuild up of static charges. Where flam-mable or explosive dust mixtures may

be present, the abrasive blasting enclo-sure, the ducts, and the dust collectorshall be constructed with loose panels

or explosion venting areas, located onsides away from any occupied area, toprovide for pressure relief in case of ex-plosion, following the principles set

forth in the National Fire ProtectionAssociation Explosion Venting Guide.NFPA 681954.

(3) Blast-cleaning enclosures. (i) Blast-cleaning enclosures shall be exhaustventilated in such a way that a contin-

uous inward flow of air will be main-tained at all openings in the enclosureduring the blasting operation.

(A) All air inlets and access openingsshall be baffled or so arranged that bythe combination of inward air flow and

baffling the escape of abrasive or dustparticles into an adjacent work areawill be minimized and visible spurts of

dust will not be observed.(B) The rate of exhaust shall be suffi-

cient to provide prompt clearance ofthe dust-laden air within the enclosureafter the cessation of blasting.

(C) Before the enclosure is opened,

the blast shall be turned off and the ex-haust system shall be run for a suffi-cient period of time to remove the

dusty air within the enclosure.(D) Safety glass protected by screen-

ing shall be used in observation win-

dows, where hard deep-cutting abra-sives are used.

(E) Slit abrasive-resistant baffles

shall be installed in multiple sets at allsmall access openings where dustmight escape, and shall be inspectedregularly and replaced when needed.

(1) Doors shall be flanged and tightwhen closed.

(2) Doors on blast-cleaning rooms

shall be operable from both inside andoutside, except that where there is asmall operator access door, the large

work access door may be closed oropened from the outside only.

(4) Exhaust ventilation systems. (i) The

construction, installation, inspection,and maintenance of exhaust systems


7/29/2019 CFR-2011-title29-vol8-sec1926-57

3/26

51


shall conform to the principles and re-

quirements set forth in American Na-tional Standard Fundamentals Gov-erning the Design and Operation of

Local Exhaust Systems, Z9.21960, andANSI Z33.11961.

(a) When dust leaks are noted, re-

pairs shall be made as soon as possible.(b) The static pressure drop at the ex-

haust ducts leading from the equip-

ment shall be checked when the instal-lation is completed and periodicallythereafter to assure continued satisfac-tory operation. Whenever an appre-

ciable change in the pressure drop indi-cates a partial blockage, the systemshall be cleaned and returned to nor-

mal operating condition.(ii) In installations where the abra-

sive is recirculated, the exhaust ven-

tilation system for the blasting enclo-sure shall not be relied upon for the re-moval of fines from the spent abrasive

instead of an abrasive separator. Anabrasive separator shall be provided forthe purpose.

(iii) The air exhausted from blast-cleaning equipment shall be dischargedthrough dust collecting equipment.

Dust collectors shall be set up so thatthe accumulated dust can be emptied

and removed without contaminatingother working areas.

(5) Personal protective equipment. (i)Employers must use only respirators

approved by NIOSH under 42 CFR part84 for protecting employees from dustsproduced during abrasive-blasting op-

erations.(ii) Abrasive-blasting respirators

shall be worn by all abrasive-blasting

operators:(A) When working inside of blast-

cleaning rooms, or

(B) When using silica sand in manualblasting operations where the nozzleand blast are not physically separatedfrom the operator in an exhaust venti-

lated enclosure, or(C) Where concentrations of toxic

dust dispersed by the abrasive blasting

may exceed the limits set in 1926.55 orother pertinent sections of this partand the nozzle and blast are not phys-

ically separated from the operator inan exhaust-ventilated enclosure.

(iii) Properly fitted particulate-filter

respirators, commonly referred to asdust-filter respirators, may be used for

short, intermittent, or occasional dust

exposures such as cleanup, dumping ofdust collectors, or unloading shipmentsof sand at a receiving point when it is

not feasible to control the dust by en-closure, exhaust ventilation, or othermeans. The respirators used must be

approved by NIOSH under 42 CFR part84 for protection against the specifictype of dust encountered.

(iv) A respiratory protection programas defined and described in 1926.103,shall be established wherever it is nec-essary to use respiratory protective

equipment.(v) Operators shall be equipped with

heavy canvas or leather gloves and

aprons or equivalent protection to pro-tect them from the impact of abra-sives. Safety shoes shall be worn to

protect against foot injury whereheavy pieces of work are handled.

(A) Safety shoes shall conform to the

requirements of American NationalStandard for Mens Safety-Toe Foot-wear, Z41.11967.

(B) Equipment for protection of theeyes and face shall be supplied to theoperator when the respirator design

does not provide such protection and toany other personnel working in the vi-

cinity of abrasive blasting operations.This equipment shall conform to therequirements of 1926.102.

(6) Air supply and air compressors. Air

for abrasive-blasting respirators mustbe free of harmful quantities of dusts,mists, or noxious gases, and must meet

the requirements for supplied-air qual-ity and use specified in 29 CFR1910.134(i).

(7) Operational procedures and general

safety. Dust shall not be permitted toaccumulate on the floor or on ledges

outside of an abrasive-blasting enclo-sure, and dust spills shall be cleaned uppromptly. Aisles and walkways shall bekept clear of steel shot or similar abra-

sive which may create a slipping haz-ard.

(8) Scope. This paragraph applies to

all operations where an abrasive isforcibly applied to a surface by pneu-matic or hydraulic pressure, or by cen-

trifugal force. It does not apply tosteam blasting, or steam cleaning, orhydraulic cleaning methods where

work is done without the aid of abra-sives.


7/29/2019 CFR-2011-title29-vol8-sec1926-57

4/26

52


(g) Grinding, polishing, and buffing op-

erations(1) Definitions applicable tothis paragraph

(i) Abrasive cutting-off wheels. Or-

ganic-bonded wheels, the thickness ofwhich is not more than one forty-eighth of their diameter for those up

to, and including, 20 inches (50.8 cm) indiameter, and not more than one-six-tieth of their diameter for those larger

than 20 inches (50.8 cm) in diameter,used for a multitude of operations var-iously known as cutting, cutting off,grooving, slotting, coping, and joint-

ing, and the like. The wheels may besolid consisting of organic-bondedabrasive material throughout, steel

centered consisting of a steel discwith a rim of organic-bonded materialmoulded around the periphery, or of

the inserted tooth type consisting ofa steel disc with organic-bonded abra-sive teeth or inserts mechanically se-

cured around the periphery.(ii) Belts. All power-driven, flexible,

coated bands used for grinding,

polishing, or buffing purposes.(iii) Branch pipe. The part of an ex-

haust system piping that is connected

directly to the hood or enclosure.(iv) Cradle. A movable fixture, upon

which the part to be ground or polishedis placed.

(v) Disc wheels. All power-driven ro-tatable discs faced with abrasive mate-

rials, artificial or natural, and used forgrinding or polishing on the side of theassembled disc.

(vi) Entry loss. The loss in static pres-sure caused by air flowing into a ductor hood. It is usually expressed in

inches of water gauge.(vii) Exhaust system. A system con-

sisting of branch pipes connected to

hoods or enclosures, one or more head-er pipes, an exhaust fan, means for sep-arating solid contaminants from theair flowing in the system, and a dis-

charge stack to outside.(viii) Grinding wheels. All power-driv-

en rotatable grinding or abrasive

wheels, except disc wheels as defined inthis standard, consisting of abrasiveparticles held together by artificial or

natural bonds and used for peripheralgrinding.

(ix) Header pipe (main pipe). A pipe

into which one or more branch pipesenter and which connects such branch

pipes to the remainder of the exhaust

system.

(x) Hoods and enclosures. The partial

or complete enclosure around the

wheel or disc through which air enters

an exhaust system during operation.

(xi) Horizontal double-spindle disc

grinder. A grinding machine carrying

two power-driven, rotatable, coaxial,

horizontal spindles upon the inside

ends of which are mounted abrasive

disc wheels used for grinding two sur-

faces simultaneously.

(xii) Horizontal single-spindle discgrinder. A grinding machine carryingan abrasive disc wheel upon one or

both ends of a power-driven, rotatablesingle horizontal spindle.

(xiii) Polishing and buffing wheels. Allpower-driven rotatable wheels com-

posed all or in part of textile fabrics,wood, felt, leather, paper, and may becoated with abrasives on the periphery

of the wheel for purposes of polishing,buffing, and light grinding.

(xiv) Portable grinder. Any power-driv-

en rotatable grinding, polishing, orbuffing wheel mounted in such mannerthat it may be manually manipulated.

(xv) Scratch brush wheels. All power-

driven rotatable wheels made fromwire or bristles, and used for scratchcleaning and brushing purposes.

(xvi) Swing-frame grinder. Any power-driven rotatable grinding, polishing, orbuffing wheel mounted in such a man-

ner that the wheel with its supportingframework can be manipulated overstationary objects.

(xvii) Velocity pressure (vp). The ki-

netic pressure in the direction of flownecessary to cause a fluid at rest toflow at a given velocity. It is usually

expressed in inches of water gauge.

(xviii) Vertical spindle disc grinder. Agrinding machine having a vertical, ro-

tatable power-driven spindle carrying a

horizontal abrasive disc wheel.(2) Application. Wherever dry grind-

ing, dry polishing or buffing is per-

formed, and employee exposure, with-out regard to the use of respirators, ex-ceeds the permissible exposure limits

prescribed in 1926.55 or other perti-nent sections of this part, a local ex-haust ventilation system shall be pro-

vided and used to maintain employeeexposures within the prescribed limits.


7/29/2019 CFR-2011-title29-vol8-sec1926-57

5/26

53


(3) Hood and branch pipe requirements.

(i) Hoods connected to exhaust systems

shall be used, and such hoods shall be

designed, located, and placed so that

the dust or dirt particles shall fall or

be projected into the hoods in the di-

rection of the air flow. No wheels,

discs, straps, or belts shall be operated

in such manner and in such direction

as to cause the dust and dirt particles

to be thrown into the operators

breathing zone.

(ii) Grinding wheels on floor stands,

pedestals, benches, and special-purposegrinding machines and abrasive cut-

ting-off wheels shall have not less than

the minimum exhaust volumes shown

in Table D57.1 with a recommended

minimum duct velocity of 4,500 feet per

minute in the branch and 3,500 feet per

minute in the main. The entry losses

from all hoods except the vertical-spin-

dle disc grinder hood, shall equal 0.65

velocity pressure for a straight takeoff

and 0.45 velocity pressure for a tapered

takeoff. The entry loss for the vertical-

spindle disc grinder hood is shown in

figure D57.1 (following paragraph (g)

of this section).

TABLE D57.1GRINDING AND ABRASIVECUTTING-OFF WHEELS

Wheel diameter, inches (cm)

Wheelwidth,inches(cm)

Minimumexhaustvolume

(feet3/min.)

To 9 (22.86) ................................... 112 (3.81) 220

Over 9 to 16 (22.86 to 40.64) ....... 2 (5.08) 390

Over 16 to 19 (40.64 to 48.26) ..... 3 (7.62) 500

Over 19 to 24 (48.26 to 60.96) ..... 4 (10.16) 610

Over 24 to 30 (60.96 to 76.2) ....... 5 (12.7) 880

Over 30 to 36 (76.2 to 91.44) ....... 6 (15.24) 1,200

For any wheel wider than wheel diame-

ters shown in Table D57.1, increase the

exhaust volume by the ratio of the new

width to the width shown.

Example: If wheel width = 412 inches (11.43

cm),

then 4.54 610 = 686 (rounded to 690).

(iii) Scratch-brush wheels and all

buffing and polishing wheels mounted

on floor stands, pedestals, benches, or

special-purpose machines shall have

not less than the minimum exhaust

volume shown in Table D57.2.

TABLE D57.2BUFFING AND POLISHINGWHEELS

Wheel diameter, inches (cm)Wheelwidth,

inches cm)

Minimumexhaustvolume

(feet3/min.)

To 9 (22.86) ................................... 2 (5.08) 300

Over 9 to 16 (22.86 to 40.64) ....... 3 (7.62) 500

Over 16 to 19 (40.64 to 48.26) ..... 4 (10.16) 610

Over 19 to 24 (48.26 to 60.96) ..... 5 (12.7) 740

Over 24 to 30 (60.96 to 76.2) ....... 6 (15.24) 1,040

Over 30 to 36 (76.2 to 91.44) ....... 6 (15.24) 1,200

(iv) Grinding wheels or discs for hori-

zontal single-spindle disc grinders shallbe hooded to collect the dust or dirt

generated by the grinding operation

and the hoods shall be connected to

branch pipes having exhaust volumes

as shown in Table D57.3.

TABLE D57.3HORIZONTAL SINGLE-SPINDLEDISC GRINDER

Disc diameter, inches (cm)Exhaustvolume

(ft.3/min.)

Up to 12 (30.48) .................................................. 220

Over 12 to 19 (30.48 to 48.26) ........................... 390

Over 19 to 30 (48.26 to 76.2) ............................. 610

Over 30 to 36 (76.2 to 91.44) ............................. 880

(v) Grinding wheels or discs for hori-zontal double-spindle disc grinders

shall have a hood enclosing the grind-

ing chamber and the hood shall be con-

nected to one or more branch pipes

having exhaust volumes as shown in

Table D57.4.

TABLE D57.4HORIZONTAL DOUBLE-SPINDLEDISC GRINDER

Disc diameter, inches (cm)Exhaustvolume

(ft.3/min.)

Up to 19 (48.26) .................................................. 610

Over 19 to 25 (48.26 to 63.5) ............................. 880

Over 25 to 30 (63.5 to 76.2) ............................... 1,200

Over 30 to 53 (76.2 to 134.62) ........................... 1,770

Over 53 to 72 (134.62 to 182.88) ....................... 6,280

(vi) Grinding wheels or discs for

vertical single-spindle disc grinders

shall be encircled with hoods to remove

the dust generated in the operation.

The hoods shall be connected to one or

more branch pipes having exhaust vol-

umes as shown in Table D57.5.


7/29/2019 CFR-2011-title29-vol8-sec1926-57

6/26

54


TABLE D57.5VERTICAL SPINDLE DISCGRINDER

Disc diameter, inches(cm)

One-half or moreof disc covered

Disc not cov-ered

Num-ber 1

Ex-haustfoot3/min.

Num-ber 1

Ex-haustfoot3/min.

Up to 20 (50.8) .......... 1 500 2 780

Over 20 to 30 (50.8 to76.2) . .. .. .. .. .. .. .. .. .. .. .. 2 780 2 1,480

Over 30 to 53 (76.2 to134.62) . .. .. .. .. .. .. .. .. .. 2 1,770 4 3,530

Over 53 to 72 (134.62to 182.88) . . .. .. .. .. .. .. . 2 3,140 5 6,010

1Number of exhaust outlets around periphery of hood, orequal distribution provided by other means.

(vii) Grinding and polishing beltsshall be provided with hoods to remove

dust and dirt generated in the oper-ations and the hoods shall be connectedto branch pipes having exhaust vol-

umes as shown in Table D57.6.

TABLE D57.6GRINDING AND POLISHINGBELTS

Belts width, inches (cm)Exhaustvolume

(ft.3/min.)

Up to 3 (7.62) ...................................................... 220

Over 3 to 5 (7.62 to 12.7) ................................... 300

Over 5 to 7 (12.7 to 17.78) ................................. 390Over 7 to 9 (17.78 to 22.86) ............................... 500

Over 9 to 11 (22.86 to 27.94) ............................. 610

Over 11 to 13 (27.94 to 33.02) ........................... 740

(viii) Cradles and swing-frame grind-

ers. Where cradles are used for han-dling the parts to be ground, polished,or buffed, requiring large partial enclo-

sures to house the complete operation,a minimum average air velocity of 150feet per minute shall be maintained

over the entire opening of the enclo-sure. Swing-frame grinders shall alsobe exhausted in the same manner as

provided for cradles. (See fig. D57.3)

(ix) Where the work is outside thehood, air volumes must be increased as

shown in American Standard Fun-damentals Governing the Design andOperation of Local Exhaust Systems,Z9.21960 (section 4, exhaust hoods).

(4) Exhaust systems. (i) Exhaust sys-tems for grinding, polishing, and buff-ing operations should be designed in

accordance with American StandardFundamentals Governing the Designand Operation of Local Exhaust Sys-

tems, Z9.21960.

(ii) Exhaust systems for grinding,

polishing, and buffing operations shallbe tested in the manner described inAmerican Standard Fundamentals

Governing the Design and Operation ofLocal Exhaust Systems, Z9.21960.

(iii) All exhaust systems shall be pro-

vided with suitable dust collectors.(5) Hood and enclosure design. (i) (A) It

is the dual function of grinding and ab-

rasive cutting-off wheel hoods to pro-tect the operator from the hazards ofbursting wheels as well as to provide ameans for the removal of dust and dirt

generated. All hoods shall be not lessin structural strength than specified inthe American National Standard Safe-

ty Code for the Use, Care, and Protec-tion of Abrasive Wheels, B7.11970.

(B) Due to the variety of work and

types of grinding machines employed,it is necessary to develop hoods adapt-able to the particular machine in ques-

tion, and such hoods shall be located asclose as possible to the operation.

(ii) Exhaust hoods for floor stands,

pedestals, and bench grinders shall bedesigned in accordance with figure D57.2. The adjustable tongue shown in

the figure shall be kept in workingorder and shall be adjusted within one-

fourth inch (0.635 cm) of the wheel pe-riphery at all times.

(iii) Swing-frame grinders shall beprovided with exhaust booths as indi-

cated in figure D57.3.(iv) Portable grinding operations,

whenever the nature of the work per-

mits, shall be conducted within a par-tial enclosure. The opening in the en-closure shall be no larger than is actu-

ally required in the operation and anaverage face air velocity of not lessthan 200 feet per minute shall be main-

tained.(v) Hoods for polishing and buffing

and scratch-brush wheels shall be con-structed to conform as closely to figure

D57.4 as the nature of the work willpermit.

(vi) Cradle grinding and polishing op-

erations shall be performed within apartial enclosure similar to figure D57.5. The operator shall be positioned

outside the working face of the openingof the enclosure. The face opening ofthe enclosure should not be any greater

in area than that actually required forthe performance of the operation and


7/29/2019 CFR-2011-title29-vol8-sec1926-57

7/26

55


the average air velocity into the work-ing face of the enclosure shall not beless than 150 feet per minute.

(vii) Hoods for horizontal single-spin-dle disc grinders shall be constructedto conform as closely as possible to thehood shown in figure D57.6. It is essen-tial that there be a space between theback of the wheel and the hood, and aspace around the periphery of thewheel of at least 1 inch (2.54 cm) inorder to permit the suction to actaround the wheel periphery. The open-ing on the side of the disc shall be no

larger than is required for the grindingoperation, but must never be less thantwice the area of the branch outlet.

(viii) Horizontal double-spindle discgrinders shall have a hood encircling

the wheels and grinding chamber simi-lar to that illustrated in figure D57.7.

The openings for passing the work into

the grinding chamber should be kept as

small as possible, but must never be

less than twice the area of the branch

outlets.

(ix) Vertical-spindle disc grinders

shall be encircled with a hood so con-

structed that the heavy dust is drawn

off a surface of the disc and the lighter

dust exhausted through a continuous

slot at the top of the hood as shown in

figure D57.1.

(x) Grinding and polishing belt hoods

shall be constructed as close to the op-eration as possible. The hood should

extend almost to the belt, and 1-inch

(2.54 cm) wide openings should be pro-

vided on either side. Figure D57.8

shows a typical hood for a belt oper-

ation.


7/29/2019 CFR-2011-title29-vol8-sec1926-57

8/26

56


Dia. D inches (cm) Exhaust E Volume Ex-hausted at4,500 ft/min

ft3/min

NoteMin. Max. No Pipes Dia.

.................................... 20 (50.8) 1 414 (10.795) 500 When one-half or more of the disccan be hooded, use exhaustducts as shown at the left.

Over 20 (50.8) ........... 30 (76.2) 2 4 (10.16) 780

Over 30 (76.2) ........... 72 (182.88) 2 6 (15.24) 1,770

Over 53 (134.62) ....... 72 (182.88) 2 8 (20.32) 3,140

.................................... 20 (50.8) 2 4 (10.16) 780 When no hood can be used overdisc, use exhaust ducts asshown at left.

Over 20 (50.8) ........... 20 (50.8) 2 4 (10.16) 780

Over 30 (76.2) . ... .... ... 30 (76.2) 2 512 (13.97) 1,480

Over 53 (134.62) ....... 53 (134.62) 4 6 (15.24) 3,530

72 (182.88) 5 7 (17.78) 6,010

Entry loss=1.0 slot velocity pressure + 0.5 branch velocity pressure.Minimum slot velocity=2,000 ft/min12-inch (1.27 cm) slot width.


7/29/2019 CFR-2011-title29-vol8-sec1926-57

9/26

57


Wheel dimension, inches (centimeters)Exhaust outlet,inches (centi-

meters) E

Volume ofair at

4,500 ft/min

DiameterWidth, Max

Min= d Max= D

9 (22.86) 112 (3.81) 3 220

Over 9 (22.86) ............................................................................. 16 (40.64) 2 (5.08) 4 390

Over 16 (40.64) ........................................................................... 19 (48.26) 3 (7.62) 412 500

Over 19 (48.26) ........................................................................... 24 (60.96) 4 (10.16) 5 610

Over 24 (60.96) ........................................................................... 30 (76.2) 5 (12.7) 6 880

Over 30 (76.2) ............................................................................. 36 (91.44) 6 (15.24) 7 1,200

Entry loss = 0.45 velocity pressure for tapered takeoff 0.65 velocity pressure for straight takeoff.


7/29/2019 CFR-2011-title29-vol8-sec1926-57

10/26

58


FIGURE D57.3A METHOD OF APPLYING AN EXHAUST ENCLOSURE TO SWING-FRAME GRINDERS

NOTE: Baffle to reduce front opening as

much as possible


7/29/2019 CFR-2011-title29-vol8-sec1926-57

11/26

59


STANDARD BUFFING AND POLISHING HOOD

Wheel dimension, inches (centimeters)

Exhaust outlet,inches E

Volume ofair at

4,500 ft/min

DiameterWidth, Max

Min= d Max= D

9 (22.86) 2 (5.08) 312 (3.81) 300

Over 9 (22.86) ............................................................................. 16 (40.64) 3 (5.08) 4 500

Over 16 (40.64) ........................................................................... 19 (48.26) 4 (11.43) 5 610

Over 19 (48.26) ........................................................................... 24 (60.96) 5 (12.7) 512 740

Over 24 (60.96) ........................................................................... 30 (76.2) 6 (15.24) 612 1.040

Over 30 (76.2) ............................................................................. 36 (91.44) 6 (15.24) 7 1.200

Entry loss = 0.15 velocity pressure for tapered takeoff; 0.65 velocity pressure for straight takeoff.


7/29/2019 CFR-2011-title29-vol8-sec1926-57

12/26

60


FIGURE D57.5CRADLE POLISHING OR GRINDING ENCLOSURE

Entry loss = 0.45 velocity pressure for

tapered takeoff


7/29/2019 CFR-2011-title29-vol8-sec1926-57

13/26

61


Dia D, inches (centimeters)Exhaust E,dia. inches

(cm)

Volume ex-hausted at

4,500 ft/minft3/min

Min. Max.

12 (30.48) 3 (7.6) 220

Over 12 (30.48) ........................................................................................................... 19 (48.26) 4 (10.16) 390

Over 19 (48.26) ........................................................................................................... 30 (76.2) 5 (12.7) 610

Over 30 (76.2) ............................................................................................................. 36 (91.44) 6 (15.24) 880

NOTE: If grinding wheels are used for disc grinding purposes, hoods must conform to structural strength and materials as de-scribed in 9.1.

Entry loss = 0.45 velocity pressure for tapered takeoff.


7/29/2019 CFR-2011-title29-vol8-sec1926-57

14/26

62


Disc dia. inches (centimeters) Exhaust E Volumeexhaust at4,500 ft/min. ft3/

min

NoteMin. Max. No Pipes Dia.

19 (48.26) 1 5 610

Over 19 (48.26) ................. 25 (63.5) 1 6 880 When width W permits, exhaustducts should be as near heaviest

grinding as possible.Over 25 (63.5) ................... 30 (76.2) 1 7 1,200

Over 30 (76.2) ................... 53 (134.62) 2 6 1,770

Over 53 (134.62) ............... 72 (182.88) 4 8 6,280

Entry loss = 0.45 velocity pressure for tapered takeoff.


7/29/2019 CFR-2011-title29-vol8-sec1926-57

15/26

63


FIGURE D57.8A TYPICAL HOOD FOR A BELT OPERATION

Entry loss = 0.45 velocity pressure fortapered takeoff

Belt width W. inches (centimeters)Exhaustvolume.ft.1/min

Up to 3 (7.62) ...................................................... 220

3 to 5 (7.62 to 12.7) ............................................ 300

5 to 7 (12.7 to 17.78) .......................................... 390

7 to 9 (17.78 to 22.86) ........................................ 500

9 to 11 (22.86 to 27.94) ...................................... 610

11 to 13 (27.94 to 33.02) .................................... 740

Minimum duct velocity = 4,500 ft/min branch, 3,500 ft/minmain.

Entry loss = 0.45 velocity pressure for tapered takeoff; 0.65velocity pressure for straight takeoff.

(6) Scope. This paragraph (g), pre-scribes the use of exhaust hood enclo-sures and systems in removing dust,

dirt, fumes, and gases generatedthrough the grinding, polishing, orbuffing of ferrous and nonferrous met-

als.

(h) Spray finishing operations(1) Defi-

nitions applicable to this paragraph(i)Spray-finishing operations. Spray-fin-ishing operations are employment of

methods wherein organic or inorganicmaterials are utilized in dispersed formfor deposit on surfaces to be coated,

treated, or cleaned. Such methods ofdeposit may involve either automatic,

manual, or electrostatic deposition butdo not include metal spraying or met-allizing, dipping, flow coating, rollercoating, tumbling, centrifuging, orspray washing and degreasing as con-

ducted in self-contained washing anddegreasing machines or systems.

(ii) Spray booth. Spray booths are de-fined and described in 1926.66(a). (See

sections 103, 104, and 105 of the Stand-ard for Spray Finishing Using Flam-

mable and Combustible Materials,NFPA No. 331969).

(iii) Spray room. A spray room is aroom in which spray-finishing oper-ations not conducted in a spray boothare performed separately from otherareas.

(iv) Minimum maintained velocity. Min-imum maintained velocity is the veloc-ity of air movement which must bemaintained in order to meet minimumspecified requirements for health and

safety.(2) Location and application. Spray

booths or spray rooms are to be used toenclose or confine all operations.Spray-finishing operations shall be lo-

cated as provided in sections 201through 206 of the Standard for SprayFinishing Using Flammable and Com-

bustible Materials, NFPA No. 331969.(3) Design and construction of spray

booths. (i) Spray booths shall be de-signed and constructed in accordance

with 1926.66(b) (1) through (4) and (6)through (10) (see sections 301304 and306310 of the Standard for Spray Fin-ishing Using Flammable and Combus-

tible Materials, NFPA No. 331969), forgeneral construction specifications.For a more detailed discussion of fun-

damentals relating to this subject, seeANSI Z9.21960

(A) Lights, motors, electrical equip-ment, and other sources of ignition

shall conform to the requirements of 1926.66(b)(10) and (c). (See section 310and chapter 4 of the Standard for Spray

Finishing Using Flammable and Com-bustible Materials NFPA No. 331969.)

(B) In no case shall combustible ma-terial be used in the construction of a


7/29/2019 CFR-2011-title29-vol8-sec1926-57

16/26

64


spray booth and supply or exhaust duct

connected to it.(ii) Unobstructed walkways shall not

be less than 612 feet (1.976 m) high and

shall be maintained clear of obstruc-tion from any work location in thebooth to a booth exit or open booth

front. In booths where the open front isthe only exit, such exits shall be notless than 3 feet (0.912 m) wide. In

booths having multiple exits, suchexits shall not be less than 2 feet (0.608m) wide, provided that the maximumdistance from the work location to the

exit is 25 feet (7.6 m) or less. Wherebooth exits are provided with doors,such doors shall open outward from the

booth.(iii) Baffles, distribution plates, and

dry-type overspray collectors shall

conform to the requirements of 1926.66(b) (4) and (5). (See sections 304and 305 of the Standard for Spray Fin-

ishing Using Flammable and Combus-tible Materials, NFPA No. 331969.)

(A) Overspray filters shall be in-

stalled and maintained in accordancewith the requirements of 1926.66(b)(5),(see section 305 of the Standard for

Spray Finishing Using Flammable andCombustible Materials, NFPA No. 33

1969), and shall only be in a locationeasily accessible for inspection, clean-ing, or replacement.

(B) Where effective means, inde-

pendent of the overspray filters, are in-stalled which will result in design airdistribution across the booth cross sec-

tion, it is permissible to operate thebooth without the filters in place.

(iv) (A) For wet or water-wash spray

booths, the water-chamber enclosure,within which intimate contact of con-taminated air and cleaning water or

other cleaning medium is maintained,if made of steel, shall be 18 gage orheavier and adequately protectedagainst corrosion.

(B) Chambers may include scrubberspray nozzles, headers, troughs, orother devices. Chambers shall be pro-

vided with adequate means for creatingand maintaining scrubbing action forremoval of particulate matter from the

exhaust air stream.(v) Collecting tanks shall be of weld-

ed steel construction or other suitable

non-combustible material. If pits areused as collecting tanks, they shall be

concrete, masonry, or other material

having similar properties.(A) Tanks shall be provided with

weirs, skimmer plates, or screens to

prevent sludge and floating paint fromentering the pump suction box. Meansfor automatically maintaining the

proper water level shall also be pro-vided. Fresh water inlets shall not besubmerged. They shall terminate at

least one pipe diameter above the safe-ty overflow level of the tank.

(B) Tanks shall be so constructed asto discourage accumulation of haz-

ardous deposits.(vi) Pump manifolds, risers, and

headers shall be adequately sized to in-

sure sufficient water flow to provide ef-ficient operation of the water chamber.

(4) Design and construction of spray

rooms. (i) Spray rooms, includingfloors, shall be constructed of masonry,concrete, or other noncombustible ma-

terial.(ii) Spray rooms shall have non-

combustible fire doors and shutters.

(iii) Spray rooms shall be adequatelyventilated so that the atmosphere inthe breathing zone of the operator

shall be maintained in accordance withthe requirements of paragraph (h)(6)(ii)

of this section.(iv) Spray rooms used for production

spray-finishing operations shall con-form to the requirements for spray

booths.(5) Ventilation. (i) Ventilation shall be

provided in accordance with provisions

of 1926.66(d) (see chapter 5 of theStandard for Spray Finishing UsingFlammable or Combustible Materials,

NFPA No. 331969), and in accordancewith the following:

(A) Where a fan plenum is used to

equalize or control the distribution ofexhaust air movement through thebooth, it shall be of sufficient strengthor rigidity to withstand the differential

air pressure or other superficially im-posed loads for which the equipment isdesigned and also to facilitate clean-

ing. Construction specifications shallbe at least equivalent to those of para-graph (h)(5)(iii) of this section.

(B) [Reserved](ii) Inlet or supply ductwork used to

transport makeup air to spray booths

or surrounding areas shall be con-structed of noncombustible materials.


7/29/2019 CFR-2011-title29-vol8-sec1926-57

17/26

65


(A) If negative pressure exists within

inlet ductwork, all seams and jointsshall be sealed if there is a possibilityof infiltration of harmful quantities of

noxious gases, fumes, or mists fromareas through which ductwork passes.

(B) Inlet ductwork shall be sized in

accordance with volume flow require-ments and provide design air require-ments at the spray booth.

(C) Inlet ductwork shall be ade-quately supported throughout itslength to sustain at least its ownweight plus any negative pressure

which is exerted upon it under normaloperating conditions.

(iii) [Reserved]

(A) Exhaust ductwork shall be ade-quately supported throughout itslength to sustain its weight plus any

normal accumulation in interior dur-ing normal operating conditions andany negative pressure exerted upon it.

(B) Exhaust ductwork shall be sizedin accordance with good design prac-tice which shall include consideration

of fan capacity, length of duct, numberof turns and elbows, variation in size,volume, and character of materials

being exhausted. See American Na-tional Standard Z9.21960 for further

details and explanation concerning ele-ments of design.

(C) Longitudinal joints in sheet steelductwork shall be either lock-seamed,

riveted, or welded. For other than steelconstruction, equivalent securing ofjoints shall be provided.

(D) Circumferential joints in duct-work shall be substantially fastenedtogether and lapped in the direction of

airflow. At least every fourth jointshall be provided with connectingflanges, bolted together, or of equiva-

lent fastening security.

(E) Inspection or clean-out doors

shall be provided for every 9 to 12 feet(2.736 to 3.648 m) of running length forducts up to 12 inches (0.304 m) in di-

ameter, but the distance betweencleanout doors may be greater for larg-er pipes. (See 8.3.21 of American Na-

tional Standard Z9.11951.) A clean-outdoor or doors shall be provided for serv-icing the fan, and where necessary, a

drain shall be provided.(F) Where ductwork passes through a

combustible roof or wall, the roof orwall shall be protected at the point of

penetration by open space or fire-resis-tive material between the duct and theroof or wall. When ducts pass through

firewalls, they shall be provided withautomatic fire dampers on both sides ofthe wall, except that three-eighth-inch

steel plates may be used in lieu ofautomatic fire dampers for ducts notexceeding 18 inches (45.72 cm) in diame-

ter.(G) Ductwork used for ventilating

any process covered in this standard

shall not be connected to ducts ven-tilating any other process or any chim-ney or flue used for conveying any

products of combustion.(6) Velocity and air flow requirements.

(i) Except where a spray booth has anadequate air replacement system, thevelocity of air into all openings of aspray booth shall be not less than that

specified in Table D57.7 for the oper-ating conditions specified. An adequateair replacement system is one which

introduces replacement air upstreamor above the object being sprayed andis so designed that the velocity of air

in the booth cross section is not lessthan that specified in Table D57.7when measured upstream or above the

object being sprayed.

TABLE D57.7MINIMUM MAINTAINED VELOCITIES INTO SPRAY BOOTHS

Operating conditions for objects completely inside booth Crossdraft,f.p.m.

Airflow velocities, f.p.m.

Design Range

Electrostatic and automatic airless operation contained in boothwithout operator.

Negligible . .. . 50 large booth . .. .. .. .. .. .. .. .. .. .. . 5075

................. 100 small booth .................... 75125

Air-operated guns, manual or automatic ............................................ Up to 50 ...... 100 large booth .................... 75125

................. 150 small booth .................... 125175

Air-operated guns, manual or automatic ............................................ Up to 100 .... 150 large booth .................... 125175

................. 200 small booth .................... 150250

NOTES:


7/29/2019 CFR-2011-title29-vol8-sec1926-57

18/26

66


(1) Attention is invited to the fact that the effectiveness of the spray booth is dependent upon the relationship of the depth ofthe booth to its height and width.

(2) Crossdrafts can be eliminated through proper design and such design should be sought. Crossdrafts in excess of100fpm (feet per minute) should not be permitted.

(3) Excessive air pressures result in loss of both efficiency and material waste in addition to creating a backlash that maycarry overspray and fumes into adjacent work areas.

(4) Booths should be designed with velocities shown in the column headed Design. However, booths operating with veloci-ties shown in the column headed Range are in compliance with this standard.

(ii) In addition to the requirementsin paragraph (h)(6)(i) of this section thetotal air volume exhausted through a

spray booth shall be such as to dilutesolvent vapor to at least 25 percent ofthe lower explosive limit of the solvent

being sprayed. An example of the meth-od of calculating this volume is givenbelow.

Example: To determine the lower explosive

limits of the most common solvents used in

spray finishing, see Table D57.8. Column 1

gives the number of cubic feet of vapor per

gallon of solvent and column 2 gives the

lower explosive limit (LEL) in percentage by

volume of air. Note that the quantity of sol-

vent will be diminished by the quantity of

solids and nonflammables contained in the

finish.To determine the volume of air in cubic

feet necessary to dilute the vapor from 1 gal-

lon of solvent to 25 percent of the lower ex-

plosive limit, apply the following formula:

Dilution volume required per gallon of

solvent=4 (100LEL) (cubic feet ofvapor per gallon) LEL

Using toluene as the solvent.

(1) LEL of toluene from Table D57.8, col-

umn 2, is 1.4 percent.(2) Cubic feet of vapor per gallon from

Table D57.8, column 1, is 30.4 cubic feet per

gallon.

(3) Dilution volume required =

4 (1001.4) 30.4 1.4=8,564 cubic feet.

(4) To convert to cubic feet per minute of

required ventilation, multiply the dilution

volume required per gallon of solvent by the

number of gallons of solvent evaporated per

minute.

TABLE D57.8LOWER EXPLOSIVE LIMIT OF

SOME COMMONLY USED SOLVENTS

Solvent

Cubic feetper gallonof vapor ofliquid at 70F (21.11

C).

Lower ex-plosive

limit in per-cent by

volume ofair at 70 F(21.11 C)

Column 1 Column 2

Acetone ......................................... 44.0 2.6Amyl Acetate ( iso) . .. .. .. .. .. .. .. .. .. .. .. .. 21.6 11.0Amyl Alcohol (n) ............................ 29.6 1.2Amyl Alcohol ( iso) . .. .. .. .. .. .. .. .. .. .. .. .. 29.6 1.2

TABLE D57.8LOWER EXPLOSIVE LIMIT OFSOME COMMONLY USED SOLVENTSContinued

Solvent

Cubic feetper gallonof vapor ofliquid at 70F (21.11

C).

Lower ex-plosive

limit in per-cent by

volume ofair at 70 F(21.11 C)

Benzene ........................................ 36.8 11.4Butyl Acetate (n) ............................ 24.8 1.7Butyl Alcohol (n) ............................ 35.2 1.4Butyl Cel losolve ............................. 24.8 1.1Cellosolve ...................................... 33.6 1.8Cellosolve Acetate ......................... 23.2 1.7Cyclohexanone ... .. .. .. .. .. .. .. .. .. .. .. .. .. . 31.2 11.11,1 Dichloroethylene ...................... 42.4 5.91,2 Dichloroethylene ...................... 42.4 9.7Ethyl Acetate ................................. 32.8 2.5Ethyl Alcohol .................................. 55.2 4.3Ethyl Lactate .................................. 28.0 11.5Methyl Acetate ............................... 40.0 3.1Methyl Alcohol ............................... 80.8 7.3Methyl Cellosolve .......................... 40.8 2.5Methyl Ethyl Ketone ... .. .. .. .. .. .. .. .. .. . 36.0 1 .8Methyl n-Propyl Ketone ... .. .. .. .. .. .. .. 30.4 1 .5Naphtha (VM&P) (76Naphtha) ..... 22.4 0.9Naphtha (100Flash) Safety Sol-

ventStoddard Solvent . .. .. .. .. .. .. 23.2 1 .0

Propyl Acetate (n) . .. .. .. .. .. .. .. .. .. .. .. .. 27.2 2 .8Propyl Acetate ( iso) ....................... 28.0 1.1Propyl Alcohol (n) .......................... 44.8 2.1Propyl Alcohol ( iso) ....................... 44.0 2.0Toluene .......................................... 30.4 1.4Turpentine ..................................... 20.8 0.8Xylene (o) ...................................... 26.4 1.0

1At 212 F (100 C).

(iii)(A) When an operator is in a

booth downstream of the object beingsprayed, an air-supplied respirator orother type of respirator approved by

NIOSH under 42 CFR part 84 for thematerial being sprayed should be usedby the operator.

(B) Where downdraft booths are pro-vided with doors, such doors shall beclosed when spray painting.

(7) Make-up air. (i) Clean fresh air,free of contamination from adjacentindustrial exhaust systems, chimneys,

stacks, or vents, shall be supplied to aspray booth or room in quantitiesequal to the volume of air exhausted

through the spray booth.(ii) Where a spray booth or room re-

ceives make-up air through self-closing

doors, dampers, or louvers, they shallbe fully open at all times when the


7/29/2019 CFR-2011-title29-vol8-sec1926-57

19/26

67


booth or room is in use for spraying.

The velocity of air through such doors,dampers, or louvers shall not exceed200 feet per minute. If the fan charac-

teristics are such that the required airflow through the booth will be pro-vided, higher velocities through the

doors, dampers, or louvers may beused.

(iii) (A) Where the air supply to a

spray booth or room is filtered, the fanstatic pressure shall be calculated onthe assumption that the filters aredirty to the extent that they require

cleaning or replacement.(B) The rating of filters shall be gov-

erned by test data supplied by the man-

ufacturer of the filter. A pressure gageshall be installed to show the pressuredrop across the filters. This gage shall

be marked to show the pressure drop atwhich the filters require cleaning or re-placement. Filters shall be replaced or

cleaned whenever the pressure dropacross them becomes excessive orwhenever the air flow through the face

of the booth falls below that specifiedin Table D57.7.

(iv) (A) Means for heating make-up

air to any spray booth or room, beforeor at the time spraying is normally

performed, shall be provided in allplaces where the outdoor temperaturemay be expected to remain below 55 F.(12.77 C.) for appreciable periods of

time during the operation of the boothexcept where adequate and safe meansof radiant heating for all operating per-

sonnel affected is provided. The re-placement air during the heating sea-sons shall be maintained at not less

than 65 F. (18.33 C.) at the point ofentry into the spray booth or sprayroom. When otherwise unheated make-

up air would be at a temperature ofmore than 10 F. below room tempera-ture, its temperature shall be regulatedas provided in section 3.6.3 of ANSI

Z9.21960.(B) As an alternative to an air re-

placement system complying with the

preceding section, general heating ofthe building in which the spray roomor booth is located may be employed

provided that all occupied parts of thebuilding are maintained at not lessthan 65 F. (18.33 C.) when the exhaust

system is in operation or the generalheating system supplemented by other

sources of heat may be employed to

meet this requirement.(C) No means of heating make-up air

shall be located in a spray booth.

(D) Where make-up air is heated bycoal or oil, the products of combustionshall not be allowed to mix with the

make-up air, and the products of com-bustion shall be conducted outside thebuilding through a flue terminating at

a point remote from all points wheremake-up air enters the building.

(E) Where make-up air is heated bygas, and the products of combustion

are not mixed with the make-up air butare conducted through an independentflue to a point outside the building re-

mote from all points where make-upair enters the building, it is not nec-essary to comply with paragraph

(h)(7)(iv)(F) of this section.(F) Where make-up air to any manu-

ally operated spray booth or room is

heated by gas and the products of com-bustion are allowed to mix with thesupply air, the following precautions

must be taken:(1) The gas must have a distinctive

and strong enough odor to warn work-

men in a spray booth or room of itspresence if in an unburned state in the

make-up air.(2) The maximum rate of gas supply

to the make-up air heater burnersmust not exceed that which would

yield in excess of 200 p.p.m. (parts permillion) of carbon monoxide or 2,000p.p.m. of total combustible gases in the

mixture if the unburned gas upon theoccurrence of flame failure were mixedwith all of the make-up air supplied.

(3) A fan must be provided to deliverthe mixture of heated air and productsof combustion from the plenum cham-

ber housing the gas burners to thespray booth or room.

(8) Scope. Spray booths or sprayrooms are to be used to enclose or con-

fine all spray finishing operations cov-ered by this paragraph (h). This para-graph does not apply to the spraying of

the exteriors of buildings, fixed tanks,or similar structures, nor to smallportable spraying apparatus not used

repeatedly in the same location.(i) Open surface tanks(1) General. (i)

This paragraph applies to all oper-

ations involving the immersion of ma-terials in liquids, or in the vapors of


7/29/2019 CFR-2011-title29-vol8-sec1926-57

20/26

68


such liquids, for the purpose of clean-

ing or altering the surface or adding toor imparting a finish thereto or chang-ing the character of the materials, and

their subsequent removal from the liq-uid or vapor, draining, and drying.These operations include washing, elec-

troplating, anodizing, pickling,quenching, dying, dipping, tanning,dressing, bleaching, degreasing, alka-

line cleaning, stripping, rinsing, digest-ing, and other similar operations.

(ii) Except where specific construc-tion specifications are prescribed in

this section, hoods, ducts, elbows, fans,blowers, and all other exhaust systemparts, components, and supports there-

of shall be so constructed as to meetconditions of service and to facilitatemaintenance and shall conform in con-

struction to the specifications con-tained in American National StandardFundamentals Governing the Design

and Operation of Local Exhaust Sys-tems, Z9.21960.

(2) Classification of open-surface tank

operations. (i) Open-surface tank oper-ations shall be classified into 16 class-es, numbered A1 to D4, inclusive.

(ii) Determination of class. Class is de-termined by two factors, hazard poten-

tial designated by a letter from A to D,inclusive, and rate of gas, vapor, ormist evolution designated by a numberfrom 1 to 4, inclusive (for example, B.3).

(iii) Hazard potential is an index, ona scale of from A to D, inclusive, of theseverity of the hazard associated with

the substance contained in the tank be-cause of the toxic, flammable, or explo-sive nature of the vapor, gas, or mist

produced therefrom. The toxic hazardis determined from the concentration,measured in parts by volume of a gas

or vapor, per million parts by volumeof contaminated air (p.p.m.), or in mil-ligrams of mist per cubic meter of air(mg./m.3), below which ill effects are

unlikely to occur to the exposed work-er. The concentrations shall be those in 1926.55 or other pertinent sections of

this part.(iv) The relative fire or explosion

hazard is measured in degrees Fahr-

enheit in terms of the closed-cup flashpoint of the substance in the tank. De-tailed information on the prevention of

fire hazards in dip tanks may be foundin Dip Tanks Containing Flammable or

Combustible Liquids, NFPA No. 341966, National Fire Protection Associa-tion. Where the tank contains a mix-ture of liquids, other than organic sol-vents, whose effects are additive, thehygienic standard of the most toxiccomponent (for example, the one hav-ing the lowest p.p.m. or mg./m.3) shallbe used, except where such substanceconstitutes an insignificantly smallfraction of the mixture. For mixturesof organic solvents, their combined ef-fect, rather than that of either individ-ually, shall determine the hazard po-

tential. In the absence of informationto the contrary, the effects shall beconsidered as additive. If the sum ofthe ratios of the airborne concentra-tion of each contaminant to the toxic

concentration of that contaminant ex-ceeds unity, the toxic concentrationshall be considered to have been ex-

ceeded. (See Note A to paragraph(i)(2)(v) of this section.)

(v) Hazard potential shall be deter-mined from Table D57.9, with thevalue indicating greater hazard being

used. When the hazardous materialmay be either a vapor with athreshhold limit value (TLV) in p.p.m.

or a mist with a TLV in mg./m.3, the

TLVindicating the greater hazard shallbe used (for example, A takes prece-

dence over B or C; B over C; C over D).

NOTE A:

(c1TLV1)+(c2TLV2)+(c3TLV3)+; . .

.(cNTLVN)1

Where:

c = Concentration measured at the operation

in p.p.m.

TABLE D57.9DETERMINATION OF HAZARDPOTENTIAL

Hazard potential

Toxicity group

Gas orvapor

(p.p.m.)

Mist (mg./m3)

Flash point indegrees F. (C.)

A .......................... 010 00.1 ..........................B .......................... 11100 0.111.0 Under 100(37.77)

C .......................... 101500 1.110 100 200(37.7793.33)

D .......................... Over 500 Over 10 Over 200(93.33)

(vi) Rate of gas, vapor, or mist evo-lution is a numerical index, on a scaleof from 1 to 4, inclusive, both of the

relative capacity of the tank toproduce gas, vapor, or mist and of the


7/29/2019 CFR-2011-title29-vol8-sec1926-57

21/26

69


relative energy with which it is pro-

jected or carried upwards from thetank. Rate is evaluated in terms of

(A) The temperature of the liquid in

the tank in degrees Fahrenheit;(B) The number of degrees Fahr-

enheit that this temperature is below

the boiling point of the liquid in de-grees Fahrenheit;

(C) The relative evaporation of the

liquid in still air at room temperaturein an arbitrary scalefast, medium,slow, or nil; and

(D) The extent that the tank gases or

produces mist in an arbitrary scalehigh, medium, low, and nil. (See TableD57.10, Note 2.) Gassing depends upon

electrochemical or mechanical proc-esses, the effects of which have to beindividually evaluated for each instal-

lation (see Table D57.10, Note 3).(vii) Rate of evolution shall be deter-

mined from Table D57.10. When evapo-

ration and gassing yield different rates,the lowest numerical value shall beused.

TABLE D57.10DETERMINATION OF RATE OF GAS, VAPOR, OR MIST EVOLUTION1

RateLiquid temperature,

F. (C.)Degrees below boil-

ing pointRelative evaporation 2 Gassing3

1 ................................ Over 200 (93.33) 020 Fast ...................................... High.2 ................................ 150200 (65.55

93.33)2150 Medium ................................ Medium.

3 ................................ 94149 (34.4465) 51100 Slow ..................................... Low.4 ................................ Under 94 (34.44) Over 100 Nil ........................................ Nil.

1 In certain classes of equipment, specifically vapor degreasers, an internal condenser or vapor level thermostat is used to pre-vent the vapor from leaving the tank during normal operation. In such cases, rate of vapor evolution from the tank into the work-room is not dependent upon the factors listed in the table, but rather upon abnormalities of operating procedure, such as carry-out of vapors from excessively fast action, dragout of liquid by entrainment in parts, contamination of solvent by water and othermaterials, or improper heat balance. When operating procedure is excellent, effective rate of evolution may be taken as 4. Whenoperating procedure is average, the effective rate of evolution may be taken as 3. When operation is poor, a rate of 2 or 1 is in-dicated, depending upon observed conditions.

2Relative evaporation rate is determined according to the methods described by A. K. Doolittle in Industrial and EngineeringChemistry, vol. 27, p. 1169, (3) where time for 100-percent evaporation is as follows: Fast: 03 hours; Medium: 312 hours;Slow: 1250 hours; Nil: more than 50 hours.

3Gassing means the formation by chemical or electrochemical action of minute bubbles of gas under the surface of the liquidin the tank and is generally limited to aqueous solutions.

(3) Ventilation. Where ventilation isused to control potential exposures toworkers as defined in paragraph(i)(2)(iii) of this section, it shall be ade-quate to reduce the concentration ofthe air contaminant to the degree thata hazard to the worker does not exist.Methods of ventilation are discussed inAmerican National Standard Fun-damentals Governing the Design andOperation of Local Exhaust Systems,Z9.21960.

(4) Control requirements. (i) Controlvelocities shall conform to Table D57.11 in all cases where the flow of airpast the breathing or working zone of

the operator and into the hoods is un-disturbed by local environmental con-ditions, such as open windows, wallfans, unit heaters, or moving machin-

ery.

(ii) All tanks exhausted by means of

hoods which

(A) Project over the entire tank;

(B) Are fixed in position in such a lo-

cation that the head of the workman,

in all his normal operating positions

while working at the tank, is in front

of all hood openings; and

(C) Are completely enclosed on at

least two sides, shall be considered to

be exhausted through an enclosing

hood.

(D) The quantity of air in cubic feet

per minute necessary to be exhausted

through an enclosing hood shall be not

less than the product of the control ve-locity times the net area of all open-

ings in the enclosure through which air

can flow into the hood.


7/29/2019 CFR-2011-title29-vol8-sec1926-57

22/26

70


TABLE D57.11CONTROL VELOCITIES IN FEET PER MINUTE (F.P.M.) FOR UNDISTURBED LOCATIONS

Class

Enclosing hoodLateral ex-

haust 1

Canopy hood 2

One openside

Two opensides

Threeopen sides

Four opensides

B1 and A2 ........................................................................... 100 150 150 Do not use Do not useA3 2, B1, B2, and C1 ....................................................... 75 100 100 125 175A3, C2, and D1 3 ............................................................... 65 90 75 100 150B4 2, C3, and D2 3 ............................................................. 50 75 50 75 125A4, C4, D3 3, and D4 4 .................................................... .................. .................. .................. .................. ..................

1See Table D57.12 for computation of ventilation rate.2Do not use canopy hood for Hazard Potential A processes.3Where complete control of hot water is desired, design as next highest class.4General room ventilation required.

(iii) All tanks exhausted by means ofhoods which do not project over the en-tire tank, and in which the direction ofair movement into the hood or hoods issubstantially horizontal, shall be con-sidered to be laterally exhausted. Thequantity of air in cubic feet per minutenecessary to be laterally exhausted persquare foot of tank area in order tomaintain the required control velocityshall be determined from Table D57.12for all variations in ratio of tank width(W) to tank length $(L). The totalquantity of air in cubic feet per minuterequired to be exhausted per tank shallbe not less than the product of the area

of tank surface times the cubic feet perminute per square foot of tank area,determined from Table D57.12.

(A) For lateral exhaust hoods over 42

inches (1.06 m) wide, or where it is de-

sirable to reduce the amount of air re-

moved from the workroom, air supply

slots or orifices shall be provided along

the side or the center of the tank oppo-

site from the exhaust slots. The design

of such systems shall meet the fol-

lowing criteria:

(1) The supply air volume plus the en-

trained air shall not exceed 50 percent

of the exhaust volume.

(2) The velocity of the supply air-

stream as it reaches the effective con-

trol area of the exhaust slot shall be

less than the effective velocity over

the exhaust slot area.

TABLE D57.12MINIMUM VENTILATION RATE IN CUBIC FEET OF AIR PER MINUTE PER SQUAREFOOT OF TANK AREA FOR LATERAL EXHAUST

Required minimum control velocity, f.p.m. (from Table D57.11)

C.f.m. per sq. ft. to maintain required minimum velocities at fol-lowing ratios (tank width (W)/tank length (L)). 1,2

0.00.09 0.10.24 0.250.49 0.50.99 1.02.0

Hood along one side or two parallel sides of tank when one hood is against a wall or baffle. 2Also for a manifold along tank centerline. 3

50 ............................................................................................ 50 60 75 90 10075 ............................................................................................ 75 90 110 130 150100 .......................................................................................... 100 125 150 175 200150 .......................................................................................... 150 190 225 260 300

Hood along one side or two parallel sides of free standing tank not against wall or baffle.

50 ............................................................................................ 75 90 100 110 12575 ............................................................................................ 110 130 150 170 190100 .......................................................................................... 150 175 200 225 250150 .......................................................................................... 225 260 300 340 375

1 It is not practicable to ventilate across the long dimension of a tank whose ratio W/L exceeds 2.0.It is undesirable to do so when W/L exceeds 1.0. For circular tanks with lateral exhaust along up to 1/2 the circumference, use

W/L=1.0; for over one-half the circumference use W/L=0.5.2Baffle is a vertical plate the same length as the tank, and with the top of the plate as high as the tank is wide. If the exhaust

hood is on the side of a tank against a building wall or close to it, it is perfectly baffled.3Use W/2 as tank width in computing when manifold is along centerline, or when hoods are used on two parallel sides of a

tank.Tank Width (W) means the effective width over which the hood must pull air to operate (for example, where the hood face is

set back from the edge of the tank, this set back must be added in measuring tank width). The surface area of tanks can fre-quently be reduced and better control obtained (particularly on conveyorized systems) by using covers extending from the upperedges of the slots toward the center of the tank.


7/29/2019 CFR-2011-title29-vol8-sec1926-57

23/26

71


(3) The vertical height of the receiv-

ing exhaust hood, including any baffle,shall not be less than one-quarter thewidth of the tank.

(4) The supply airstream shall not beallowed to impinge on obstructions be-tween it and the exhaust slot in such a

manner as to significantly interferewith the performance of the exhausthood.

(5) Since most failure of push-pullsystems result from excessive supplyair volumes and pressures, methods ofmeasuring and adjusting the supply air

shall be provided. When satisfactorycontrol has been achieved, the adjust-able features of the hood shall be fixed

so that they will not be altered.(iv) All tanks exhausted by means of

hoods which project over the entire

tank, and which do not conform to thedefinition of enclosing hoods, shall beconsidered to be overhead canopy

hoods. The quantity of air in cubic feetper minute necessary to be exhaustedthrough a canopy hood shall be not less

than the product of the control veloc-ity times the net area of all openingsbetween the bottom edges of the hood

and the top edges of the tank.(v) The rate of vapor evolution (in-

cluding steam or products of combus-tion) from the process shall be esti-mated. If the rate of vapor evolution isequal to or greater than 10 percent of

the calculated exhaust volume re-quired, the exhaust volume shall be in-creased in equal amount.

(5) Spray cleaning and degreasing.Wherever spraying or other mechanicalmeans are used to disperse a liquid

above an open-surface tank, controlmust be provided for the airbornespray. Such operations shall be en-

closed as completely as possible. Theinward air velocity into the enclosureshall be sufficient to prevent the dis-charge of spray into the workroom.

Mechanical baffles may be used to helpprevent the discharge of spray. Spraypainting operations are covered by

paragraph (h) of this section.(6) Control means other than ventila-

tion. Tank covers, foams, beads, chips,

or other materials floating on the tanksurface so as to confine gases, mists, orvapors to the area under the cover or

to the foam, bead, or chip layer; or sur-face tension depressive agents added to

the liquid in the tank to minimize mist

formation, or any combination thereof,may all be used as gas, mist, or vaporcontrol means for open-surface tank

operations, provided that they effec-tively reduce the concentrations ofhazardous materials in the vicinity of

the worker below the limits set in ac-cordance with paragraph (i)(2) of thissection.

(7) System design. (i) The equipmentfor exhausting air shall have sufficientcapacity to produce the flow of air re-quired in each of the hoods and open-

ings of the system.(ii) The capacity required in para-

graph (i)(7)(i) of this section shall be

obtained when the airflow producingequipment is operating against the fol-lowing pressure losses, the sum of

which is the static pressure:(A) Entrance losses into the hood.(B) Resistance to airflow in branch

pipe including bends and trans-formations.

(C) Entrance loss into the main pipe.

(D) Resistance to airflow in mainpipe including bends and trans-formations.

(E) Resistance of mechanical equip-ment; that is, filters, washers, con-

densers, absorbers, etc., plus their en-trance and exit losses.

(F) Resistance in outlet duct and dis-charge stack.

(iii) Two or more operations shall notbe connected to the same exhaust sys-tem where either one or the combina-

tion of the substances removed mayconstitute a fire, explosion, or chem-ical reaction hazard in the duct sys-

tem. Traps or other devices shall beprovided to insure that condensate inducts does not drain back into any

tank.(iv) The exhaust system, consisting

of hoods, ducts, air mover, and dis-charge outlet, shall be designed in ac-

cordance with American NationalStandard Fundamentals Governing theDesign and Operation of Local Exhaust

Systems, Z9.21960, or the manual, In-dustrial Ventilation, published by theAmerican Conference of Governmental

Industrial Hygienists 1970. Airflow andpressure loss data provided by the man-ufacturer of any air cleaning device

shall be included in the design calcula-tions.


7/29/2019 CFR-2011-title29-vol8-sec1926-57

24/26

72


(8) Operation. (i) The required airflow

shall be maintained at all times during

which gas, mist, or vapor is emitted

from the tank, and at all times the

tank, the draining, or the drying area

is in operation or use. When the system

is first installed, the airflow from each

hood shall be measured by means of a

pitot traverse in the exhaust duct and

corrective action taken if the flow is

less than that required. When the prop-

er flow is obtained, the hood static

pressure shall be measured and re-

corded. At intervals of not more than 3

months operation, or after a prolonged

shutdown period, the hoods and duct

system shall be inspected for evidence

of corrosion or damage. In any case

where the airflow is found to be less

than required, it shall be increased to

the required value. (Information on air-

flow and static pressure measurement

and calculations may be found in

American National Standard Funda-

mental Governing the Design and Oper-

ation of Local Exhaust Systems, Z9.2

1960, or in the manual, Industrial Ven-

tilation, published by the American

Conference of Governmental Industrial

Hygienists.)

(ii) The exhaust system shall dis-charge to the outer air in such a man-

ner that the possibility of its effluent

entering any building is at a minimum.

Recirculation shall only be through a

device for contaminant removal which

will prevent the creation of a health

hazard in the room or area to which

the air is recirculated.

(iii) A volume of outside air in the

range of 90 percent to 110 percent of the

exhaust volume shall be provided to

each room having exhaust hoods. The

outside air supply shall enter the work-

room in such a manner as not to be

detrimental to any exhaust hood. The

airflow of the makeup air system shall

be measured on installation. Correctiveaction shall be taken when the airflow

is below that required. The makeup air

shall be uncontaminated.

(9) Personal protection. (i) All employ-

ees working in and around open-surface

tank operations must be instructed as

to the hazards of their respective jobs,

and in the personal protection and first

aid procedures applicable to these haz-

ards.

(ii) All persons required to work in

such a manner that their feet may be-come wet shall be provided with rubberor other impervious boots or shoes,

rubbers, or wooden-soled shoes suffi-cient to keep feet dry.

(iii) All persons required to handle

work wet with a liquid other thanwater shall be provided with gloves im-pervious to such a liquid and of a

length sufficient to prevent entrance ofliquid into the tops of the gloves. Theinterior of gloves shall be kept freefrom corrosive or irritating contami-

nants.(iv) All persons required to work in

such a manner that their clothing may

become wet shall be provided with suchaprons, coats, jackets, sleeves, or othergarments made of rubber, or of other

materials impervious to liquids otherthan water, as are required to keeptheir clothing dry. Aprons shall extend

well below the top of boots to preventliquid splashing into the boots. Provi-sion of dry, clean, cotton clothing

along with rubber shoes or short bootsand an apron impervious to liquidsother than water shall be considered a

satisfactory substitute where smallparts are cleaned, plated, or acid

dipped in open tanks and rapid work isrequired.

(v) Whenever there is a danger ofsplashing, for example, when additions

are made manually to the tanks, orwhen acids and chemicals are removedfrom the tanks, the employees so en-

gaged shall be required to wear eithertight-fitting chemical goggles or an ef-fective face shield. See 1926.102.

(vi) When, during the emergenciesspecified in paragraph (i)(11)(v) of thissection, employees must be in areas

where concentrations of air contami-nants are greater than the limits setby paragraph (i)(2)(iii) of this sectionor oxygen concentrations are less than

19.5 percent, they must use respiratorsthat reduce their exposure to a levelbelow these limits or that provide ade-

quate oxygen. Such respirators mustalso be provided in marked, quickly-ac-cessible storage compartments built

for this purpose when the possibilityexists of accidental release of haz-ardous concentrations of air contami-

nants. Respirators must be approved byNIOSH under 42 CFR part 84, selected


7/29/2019 CFR-2011-title29-vol8-sec1926-57

25/26

73


by a competent industrial hygienist or

other technically-qualified source, andused in accordance with 29 CFR1926.103.

(vii) Near each tank containing a liq-uid which may burn, irritate, or other-wise be harmful to the skin if splashed

upon the workers body, there shall bea supply of clean cold water. The waterpipe (carrying a pressure not exceeding

25 pounds (11.325 kg)) shall be providedwith a quick opening valve and at least48 inches (1.216 m) of hose not smallerthan three-fourths inch, so that no

time may be lost in washing off liquidsfrom the skin or clothing. Alter-natively, deluge showers and eye

flushes shall be provided in cases whereharmful chemicals may be splashed onparts of the body.

(viii) Operators with sores, burns, orother skin lesions requiring medicaltreatment shall not be allowed to work

at their regular operations until so au-thorized by a physician. Any smallskin abrasions, cuts, rash, or open

sores which are found or reported shallbe treated by a properly designatedperson so that chances of exposures to

the chemicals are removed. Workersexposed to chromic acids shall have a

periodic examination made of the nos-trils and other parts of the body, to de-tect incipient ulceration.

(ix) Sufficient washing facilities, in-

cluding soap, individual towels, andhot water, shall be provided for all per-sons required to use or handle any liq-

uids which may burn, irritate, or oth-erwise be harmful to the skin, on thebasis of at least one basin (or its equiv-

alent) with a hot water faucet for every10 employees. See 1926.51(f).

(x) Locker space or equivalent cloth-

ing storage facilities shall be providedto prevent contamination of streetclothing.

(xi) First aid facilities specific to the

hazards of the operations conductedshall be readily available.

(10) Special precautions for cyanide.

Dikes or other arrangements shall beprovided to prevent the possibility ofintermixing of cyanide and acid in the

event of tank rupture.(11) Inspection, maintenance, and in-

stallation. (i) Floors and platforms

around tanks shall be prevented frombecoming slippery both by original

type of construction and by frequent

flushing. They shall be firm, sound, and

of the design and construction to mini-

mize the possibility of tripping.

(ii) Before cleaning the interior of

any tank, the contents shall be drained

off, and the cleanout doors shall be

opened where provided. All pockets in

tanks or pits, where it is possible for

hazardous vapors to collect, shall be

ventilated and cleared of such vapors.

(iii) Tanks which have been drained

to permit employees to enter for the

purposes of cleaning, inspection, or

maintenance may contain atmospheres

which are hazardous to life or health,

through the presence of flammable or

toxic air contaminants, or through the

absence of sufficient oxygen. Before

employees shall be permitted to enter

any such tank, appropriate tests of the

atmosphere shall be made to determine

if the limits set by paragraph (i)(2)(iii)

of this section are exceeded, or if the

oxygen concentration is less than 19.5

percent.

(iv) If the tests made in accordance

with paragraph (i)(11)(iii) of this sec-

tion indicate that the atmosphere in

the tank is unsafe, before any em-

ployee is permitted to enter the tank,the tank shall be ventilated until the

hazardous atmosphere is removed, and

ventilation shall be continued so as to

prevent the occurrence of a hazardous

atmosphere as long as an employee is

in the tank.

(v) If, in emergencies, such as rescue

work, it is necessary to enter a tank

which may contain a hazardous atmos-

phere, suitable respirators, such as

self-contained breathing apparatus;

hose mask with blower, if there is a

possibility of oxygen deficiency; or a

gas mask, selected and operated in ac-

cordance with paragraph (i)(9)(vi) of

this section, shall be used. If a con-

taminant in the tank can cause derma-titis, or be absorbed through the skin,

the employee entering the tank shall

also wear protective clothing. At least

one trained standby employee, with

suitable respirator, shall be present in

the nearest uncontaminated area. The

standby employee must be able to com-

municate with the employee in the

tank and be able to haul him out of the

tank with a lifeline if necessary.


7/29/2019 CFR-2011-title29-vol8-sec1926-57

26/26

74


(vi) Maintenance work requiring

welding or open flame, where toxicmetal fumes such as cadmium, chro-mium, or lead may be evolved, shall be

done only with sufficient local exhaustventilation to prevent the creation of ahealth hazard, or be done with res-

pirators selected and used in accord-ance with paragraph (i)(9)(vi) of thissection. Welding, or the use of open

flames near any solvent cleaningequipment shall be permitted

CFR-2011-title29-vol8-sec1926-57

Documents

Transcript of CFR-2011-title29-vol8-sec1926-57